Sediment Management Systems (SMSs)

Sediment Management Systems/International Port & Shipping Industry

Dr Kirby is the co-inventor of the Nautical Depth concept (first demonstrated November 1974), now called “Passive Nautical Depth”. The Nautical Depth is the elevation defined by an appropriate rheological parameter within a fluid mud suspension above which it is safe for a vessel to sail. It was accepted and promulgated for international use by PIANC from 1983. This has spread and been taken up at many muddy ports around the world. He is now closely associated with the refinement to this method which started in 1990, called “Active Nautical Depth”.

The word “Passive” relates to naturally-occurring fluid mud suspensions, whereas “Active” involves deliberately “inducing navigability” by fluidising bed deposits in- situ using a dedicated vessel at sites not naturally prone to fluid mud encroachment.

At the world’s biggest muddy ports (ie. Rotterdam) £billions of savings and earnings have arisen from its adoption. Taking up these methods would result in commensurate benefit at smaller ports.

Dr Kirby is also the co-developer of passive “Entrance Flow Optimisation Systems” (Current Deflecting Walls, sills and berms) built at the entrances to semi-enclosed harbour basins in order to manipulate flows in a number of ways and reduce fine sediment encroachment and settlement in these facilities.

EFOS installations have been built at the entrances to large harbour basins in Hamburg (Köhlfleet) and Antwerp (Deurganckdok) where they have significantly reduced dredging need over short payback times.

In respect of these modern generic sediment management systems, Dr Kirby has been closely involved in the design and application of 3 generations of high speed, high range optical siltmeters (see below)..

He was closely involved (from 1972-3) in developing continuous vertical profiling gamma-ray backscatter and transmissance densimeters which were the earliest devices used to establish Nautical Depth (see below)..

Later he developed a towed undulating high speed gamma-transmissance densimeter, the “Navitracker” (1986-present) (see below)..

Similarly, Dr Kirby was closely involved in developing the “Sediview” software to measure suspended sediment concentration underway using an RDI ADCP. Currently, via close links to German co-workers, he advises on more modern and appropriate parameters concerning dynamic resistance – sheer strength and viscosity, by which to determine nautical depth.

The first 35 years experience, coupled with equipment needed to design, build and verify these and other generic Sediment Management Systems, was set out in PIANC Report 102 “Minimising Harbour Siltation” – a Working Group chaired by Dr Kirby.

Implementing these technologies leads directly to great cost saving by depth increases and high benefit from greater earning capacity. Each of these technologies is associated with major environmental benefit. These are anti-siltation rather than dredging technologies and, as such, do not require a dredging or disposal licence.


Modern high speed vertical silt/salinity/temperature v. depth profiler


(a) Twin probe gamma-ray transmission densimeters and single probe gamma-ray backscatter densimeters specified by IOS and built by AERE, Harwell. When combined with a pressure sensor as in (b), both devices have been used to measure continuous vertical density profiles in high concentration suspensions.

Prototype Navitracker system designed by Ravensrodd Consultants Ltd. Intelligent winch with deployment A-frame (left) and tow-fish (right)